1. Field of the Invention
This invention relates to microstrip transmission lines and microstrip transmission line components operating in the millimeter wave region of the frequency spectrum and more particularly to a microstrip nonreciprocal phase for use with such microstrip transmission lines and microstrip components.
2. Description of the Prior Art
Nonreciprocal phase shifters are devices employed to perform a nonreciprocal phase shift function in many types of RF circuits. For example, in the millimeter wave region of the frequency spectrum, nonreciprocal phase shifters are employed with phased antenna arrays for radar and communications applications, four-port switchable circulators, switches and power dividers. Since much of the equipment in this region of the frequency spectrum is designed with planar circuitry utilizing microstrip transmission lines and components, a need has arisen for a suitable microstrip nonreciprocal phase shifter which is capable of being used with this equipment. Although nonreciprocal phase shifters of the "twin slab" ferrite type have been developed for use with microwave applications utilizing the hollow, metallic waveguide transmission medium, there is presently not available a millimeter wave nonreciprocal phase shifter which is suitable for use with the aforementioned planar circuitry which uses the microstrip transmission line medium. Since the microstrip transmission components used in applications in the millimeter wave region of the frequency spectrum are of extremely small size and low weight, they are often difficult to fabricate and assemble using automated techniques. Accordingly, a suitable nonreciprocal microstrip phase shifter for use in this region of the frequency spectrum should be capable of being fabricated relatively easily and inexpensively and of being installed in the planar circuit applications relatively easily and inexpensively to minimize overall equipment cost. Additionally, a suitable nonreciprocal microstrip phase shifter should also exhibit a relatively low insertion loss in this region of the frequency spectrum.